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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
1046 PM CDT Thursday Jul 10 2014

Short term...(this evening through friday)
issued at 325 PM CDT Thursday Jul 10 2014

Main concern for the short term is turning out to be the potential
for heavy rain tonight over western Minnesota based on latest hi-res cams.

This afternoon...srly low level winds have become well established
as high pressure has now pushed off to Michigan. These srly winds
have finally brought the Canadian smoke plume that was lingering
just to our SW the past couple of days up into central and southern
Minnesota...hence the milky color in the sky and occasional haze reports
across the area this afternoon. Back to the west...a short wave can
be seen approaching western Minnesota...though this has done nothing more than
create mainly virga...and this is expected to be the case as it
works across Minnesota this evening. Instead...the main wave driving the
weather across the northern plains is the cut-off 500 mb low currently
spinning from Alberta into Saskatchewan. This wave is what is
forcing the low level jet to be back more across central into the eastern Dakotas
today.

For this afternoon into tonight...favored the forecast for probability of precipitation and
quantitative precipitation forecast toward the rap/European model (ecmwf) along with just about any hi-res cam you
can find that was run at 12z or later. All of these models show
thunderstorms developing over NE sodak around 21/22z and slowly
working east into western Minnesota this evening. All hi-res models show 2-4
inches of rain falling in the generally vicinity of the NE sodak/western Minnesota
border. Looking at the rap...this looks to be tied to what is
happening in the 925-850mb layer. The rap has been pretty consistent
with showing moisture transport in this layer increasing this
afternoon across southeast sodak...with the edge of it up into NE sodak. In
addition to that...the rap shows a strong fgen signal at the nose of
this low level jet. The reason for the heavy precipitation signal is this low level jet and its
associated fgen remain more or less stationary out near the Minnesota/South Dakota
border through about 6z. With this forcing remaining
stationary...there will be a period through about 6z where the
activity can train out there...before everything starts to become
more progressive late tonight as the Canadian upper low moves toward
Manitoba. Quantitative precipitation forecast grids used were a blend of the short term cams
tempered with the 12z European model (ecmwf). This resulted in 1-2 inches of quantitative precipitation forecast
through Friday morning out in western Minnesota...which may still be conservative
considering some of the hi-res models have been showing the
potential for isolated rainfall amounts over 5 inches tonight...so
this is something that certainly bears some watching.

Through the rest of the short term...the low level jet and surface front will
slowly work east with time during the morning on Friday...with best
rainfall chances for eastern Minnesota/western WI likely coming during the morning
as remnants of tonights activity shifts east. Backed off some on
probability of precipitation Friday afternoon...as cams are fairly sparse with activity as
we loose the definition on the surface front...which will coincide with
a weakening of the low level jet as we get into subsidence associated with the
right entrance region of the upper jet working across the
international border. With less activity expected...also boosted
temperatures a few degrees out in western WI as it is not looking as likely for
Friday to be dominated by clouds and rain as was previously
anticipated.

Long term...(friday night through thursday)
issued at 325 PM CDT Thursday Jul 10 2014

As we progress through the Saturday-Thursday period we/ll see quite
the evolution of large scale features and weather across the area.
Things will start out warm with the upper jet north of the area...
but an unseasonably deep upper low will drop south/east from central
Canada into the upper Midwest and Great Lakes region during the
Sunday night through Tuesday period. This will bring very cool
temperatures to much of the region... with The Heart of the cold air
tracking across Minnesota and points east. Some precipitation chances will
loiter across the region Saturday into Sunday prior to the arrival
of the cold front and upper trough... with diurnal chances for precipitation
after that as the upper cold pool swings across the region. Best
chances for precipitation prior to frontal passage will be across the southern portions
of the area where the baroclinic zone and best instability are
prognosticated... with chances for diurnal rain showers following frontal passage located
over eastern areas where boundary layer cyclonic flow will be most
prevalent and low-middle level lapse rates will be steepest beneath the
middle-upper level cold pool. We will see ridging begin to work into
the area after Tuesday... with dry weather and moderating
temperatures for the last few days of the forecast period.

&&

Aviation...(for the 06z tafs through 06z Friday night)
issued at 1046 PM CDT Thursday Jul 10 2014

Showers and isolated thunderstorms are increasing late this
evening across central areas of Minnesota. This activity is expected to
expand south and toward krwf and kstc by 09z. Still appears to be
a few hours of on and off showers and thunderstorms. The picture
is not as clear for the Twin Cities and points east. It may take
until around 12z for any substantial showers to reach kmsp and
through 16z on over to Keau. Confidence has increased enough to
indicate a few hours of MVFR ceilings (025-030) at kaxn...kstc and
krwf Friday morning in the moist southerly flow. Lowest indicated
ceilings for kmsp and points east on Friday was 035. Much of the
rain showers/thunderstorms and rain activity should be over by Friday afternoon with the
exception of Keau where a prob30 group was used.

Kmsp...organized showers and a few thunderstorms not expected
until after 11z. Scattered showers and near MVFR ceilings (035)
indicated for the late morning with dry conditions thereafter.

/Outlook for kmsp/
Sat...VFR with MVFR/shra/tsra possible. Wind northwest at 5 kts.
Sun...VFR with MVFR/shra/tsra possible. Winds west at 5-10 kts.
Monday...VFR with MVFR ceilings/rain showers possible. Wind northwest at 10-20 kts.

&&

Mpx watches/warnings/advisories...
Minnesota...none.
WI...none.
&&

$$

Short term...mpg
long term...trh
aviation...rah

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